Recently, in a process of manufacturing a semiconductor device, for example, the diameter increase and thickness reduction of a substrate such as, for example, a silicon wafer or a compound semiconductor wafer, is progressing. A large and thin substrate may be warped or cracked during conveyance or polishing. Therefore, the conveyance or polishing is performed after gluing a separate substrate to the substrate to reinforce the substrate, and then a peeling process is performed so as to separate the substrates from each other. Further, in order to form a peeling start point when peeling the substrates from each other, a blade is inserted between the substrates to form a notch (see, e.g., Japanese Patent Laid-Open Publication No. 2014-165281).